The present invention relates to an intake manifold of an internal combustion engine, and in particular to a sealing arrangement for an intake manifold of an internal combustion engine.
A V-type engine comprises a pair of cylinder banks, and the intake ports are typically provided on the sides of the cylinder banks facing each other. Therefore, an intake manifold is typically provided between the two cylinder banks, and communicate with the intake ports via intake passages extending toward or away from the crankshaft of the engine. Sometimes, the intake manifold is provided with intake passages having a prescribed length for effecting an inertia supercharging and a surge tank having a prescribed volume for effecting a resonance supercharging (See Japanese patent laid open publication No. 8-14126).
According to the invention disclosed in this Japanese paten publication, the intake passages are defined by first intake pipes extending from the intake ports and second intake pipes extending between the upstream end of the first intake pipes and a surge tank. The first intake pipes are joined to each other by flanges at both ends so as to form an integral unit for each cylinder bank. The second intake pipes are integrally formed with the surge tank. Therefore, in this case, the intake manifold essentially consists of three major pieces. The first intake pipes are joined to the second intake pipes by threaded bolts which are passed through the radial flanges provided on the opposing ends thereof. According to this conventional arrangement, the surge tank is configured so as not to interfere with the fastening of these threaded bolts.
In recent years, there is a growing demand to minimize the size of the engine while maximizing the performance of the engine. For instance, the engines for outboard marine drives are required to be contained in a limited space of a cowling. In such a case, the size of the surge tank is often desired to be increased for an optimum resonance effect to such an extent that the surge tank may interfere with the fastening of the threaded bolts for joining the two parts of the intake manifold.
To avoid this problem, it is conceivable to increase the size of the flange, but it leads to the problems associated with sealing, and availability of space around the engine. Alternatively, the threaded bolts may be allowed to be passed across the mounting surfaces of the two parts from the interior of the surge tank. However, it will require not only to provide a removable cover to the top wall of the surge tank to permit access to the threaded bolts but also to provide a sealing arrangement in an interface between the two parts of the intake manifold for preventing leakage of air or negative pressure via the mounting holes for receiving the threaded bolts. Also, the threaded holes receiving the threaded bolts would cause leakage of air or negative pressure along a spiral path if they are formed as through holes.
When the intake manifold is formed by injection molded or otherwise prepared plastic material, it is often necessary to form the intake manifold out of a plurality of pieces. In such a case, it is necessary to design the intake manifold so as to permit access for the tools that are required for assembling and removing the intake manifold. This requirement places a severe restriction on the freedom in designing the intake manifold.
In view of such problems of the prior art, a primary object of the present invention is to provide an intake manifold of an internal combustion engine which is suited to be molded from plastic material.
A second object of the present invention is to provide an intake manifold of an internal combustion engine which is simple and economical.
A third object of the present invention is to provide an intake manifold of an internal combustion engine which allows the intake manifold incorporated with a surge tank to be assembled to the engine without being interfered by the surge tank.
A fourth object of the present invention is to provide an intake manifold of an internal combustion engine which allows a surge tank having a relatively large volume to be achieved without detracting from the compact design of the engine.
According to the present invention, these and other objects can be accomplished by providing an intake manifold for an internal combustion engine, comprising: an intake pipe assembly including at least one intake pipe defining an intake passage having a downstream end attached to an intake port of the engine and an upstream end defining an end surface, the end surface being provided with a plurality of threaded blind holes; a surge tank assembly including a bottom wall, peripheral wall and upper wall jointly defining a chamber having a certain volume therein, the chamber including a downstream end abutting the end surface at the upstream end of the intake pipe and an upstream end connected to a throttle body for introducing intake air into the chamber in a controlled manner, the bottom wall being provided with a mating surface adapted to the end surface and mounting through holes corresponding to the threaded blind holes; threaded bolts passed through the mounting through holes from inside the chamber and threaded into the threaded blind holes to securely connect the downstream end of the chamber with the upstream end of the intake pipe; and a seal member interposed between the end surface of the intake pipe and the mating surface of the surge tank assembly so as to seal off the intake passage and mounting holes individually.
Thus, the seal member, combined with the use of the blind threaded holes, ensures the sealing of both the intake passages and mounting holes at the interface between the end surface of the intake pipe and the mating surface of the surge tank assembly in a both reliable and simple manner. Preferably, the seal member comprises an O-ring made of elastomeric material, and at least one of the mating surface and end surface is provided with a groove for receiving the seal member. The O-ring provides a favorable sealing even when the contact pressure between the two surfaces is not significant so that the various components of the intake manifold can be made of plastic or other relatively soft or deformable material without creating any problem. The seal member may also comprise a gasket that individually seals off the intake passages and mounting holes.
If the engine comprises a plurality of cylinders, the seal member may comprise a main part surrounding each intake passage, a connecting part connecting adjacent main parts, and a peripheral part extending along periphery of an interface between the end surface and mating surface and joining the main parts of the seal member, the threaded bolts being passed through between the main parts and peripheral part of the seal member.
A spacer member may be interposed between the mating surface and end surface, the spacer member being provided with through holes corresponding to the intake passage and mounting through holes. This increases the choice of the materials for the various parts of the intake manifold, and simplifies the fabrication of the various parts. The groove for receiving the sealing member may be formed on a side of the spacer member.
According to a preferred embodiment of the present invention, at least most part of the surge tank assembly is made of plastic material to reduced the weight of the intake manifold. If necessary, at least most part of the intake pipe assembly is made of metallic member so that the overall mechanical strength may be ensured.
The top wall of the surge tank assembly is preferably provided with an opening for permitting access to a head of each of the threaded bolts, and a lid member for detachably closing the opening. In such a case, the lid member may be provided with a relatively high rigidity so that the overall rigidity of the surge tank may be ensured without increasing the overall weight. When the bottom wall of the surge tank assembly is made of plastic material, the mounting through hole may be defined by a metallic collar securely fitted into the bottom wall. This provides an adequate resistance or mechanical strength against the axial forces of the threaded bolts.
The surge tank assembly may comprise an intake pipe extension formed in the downstream end of the chamber, the intake pipe extension being provided with a downstream end communicating with the upstream end of the intake pipe, and an upstream end opening out inside the chamber. The intake pipe extension, in cooperation with the intake pipe, provides a relatively large length for the intake passage so as to achieve a desired inertia supercharging effect.